1. Field of the Invention
The present invention relates to gas filtering devices and in particular to a dirty gas inlet arrangement for a filter baghouse.
2. Description of the Prior Art
The prior art discloses a variety of dirty gas inlet arrangements for conducting a dirty gas stream into the dirty gas chambers of each of the filter baghouses in a baghouse installation. Both butterfly and bullseye type dampers have commonly been used for this purpose. However, in baghouse installations utilizing butterfly dampers to regulate the dirty gas flow, experience has shown it usually is very difficult to completely seal off the inlet duct for maintenance or filter cleaning operations. Consequently, it has often been the practice to use round bullseye type dampers such as disclosed in U.S. Pat. No. 3,834,662 for this purpose as that type of arrangement has proven to be more effective in sealing off the dirty gas ducts connecting the dirty gas chambers to the dirty gas manifold of the baghouse installation. As shown in FIG. 1 entitled "Prior Art", this type of arrangement typically includes a round bullseye damper 1 which is mounted in a square inlet duct 2 opening into the dirty gas chamber 3 of a filter housing 4 which includes a blade 5 which is adapted to be raised to close off an outlet 6 from a dirty gas manifold 7, and lowered to the position shown in the drawing to allow dirty gases to flow into the dirty gas chamber from the dirty gas manifold. While this arrangement has been satisfactory in many applications, it has resulted in high inlet velocities in the dirty gas stream as it enters the dirty gas chamber necessitating the installation of a baffle or similar flow distributing device within the dirty gas chamber to adequately distribute the flow across the chamber to maintain a uniform gas flow through the filter bags. Additionally, the cross-section of the inlet duct in this type of arrangement necessary to provide sufficient clearance for the blade when the damper is opened has also created regions of reduced circulation in the inlet duct where particulates tend to separate out of the dirty gas flow and accummulate in the duct.